Which V bit angle should I use for a V inlay: 90, 60, 30 or 15 degrees?

What the angle changes

A V bit cuts wider as it goes deeper. A narrow part of the design can only be carved as deep as its width allows for that angle. With a wide angle (90 degrees) a thin line ends up very shallow, so the matching plug ridge is short and has almost no glue wall. A steeper bit (30 or 15 degrees) reaches useful depth in the same thin line. The price is that steep walls forgive less: small errors in Z zero, bit angle or flatness show up as fit problems, and thin standing ridges in the pocket get fragile.

What published sources recommend

• 90 degrees: friendlier for large, bold graphics and thin stock. One guide pairs it with a flat depth of 0.125 inch and stock at least 0.25 inch thick.
• 60 degrees: the common general choice. Balances speed and glue surface for broad designs, and holds small serifs better than 90. The same guide suggests at least 0.5 inch stock for deeper 60 degree work.
• 30 degrees: suggested for detailed or fine-line artwork. Several cutting board makers use it as their default.
• 15 degrees: for extreme detail. One school's guide keeps total cutting depth shallow with it (under about 4 mm).
• A public user forum for another CNC brand reports the same trend from experience: results improve as the angle gets smaller, with 90 not worth trying on fine work and 20 to 30 degrees working well.

How to choose

1. Find the thinnest line or gap in the artwork with the measure tool.
2. If everything is bold, pick 60 (or 90 for big shapes in thin stock).
3. If thin strokes, script text or small serifs matter, drop to 30.
4. Only go to 15 when 30 still cannot reach depth, and keep the pocket shallow.
5. Use the identical bit for pocket and plug. The official documentation requires the same V bit for both halves, and says to delete and regenerate both if you change tools.

Pro tips

• Measure the real angle of a new bit on a scrap carve. A bit sold as 60 degrees that is slightly off will leave a consistent gap.
• A fresh, sharp bit matters more than the angle. A dull tip breaks fibers at the rim and reads as a gap.
• See the entry on smallest inlay detail for line-width numbers by bit.